Garnett was expected to start after missing the previous five games due to back spasms. Instead, rookie center Mason Plumlee was on the floor for the start of Monday night's game.
The 37-year-old Garnett is averaging 6.7 points in 49 games this season.
Brooklyn also was without reserve forward Andrei Kirilenko, who left Sunday night's game against Sacramento with a sprained right ankle.
The Nets did have Paul Pierce in their starting lineup after the forward left Sunday night's game with a sore shoulder.